The harrowing pictures and videos that online content moderators are watching are leaving some workers so traumatised that their hair is falling out, they are suffering from PTSD and some are even unable to shake people's hands.

The graphic content is so disturbing that one mum is afraid to leave her kids with anyone because of the things she has seen.

Another woman who had to watch child pornography can no longer think about sex.

The moderators, described as 'janitors of the internet', quietly sweep up social media, viewing the 'worst imaginable' so you and I don't have to see it. They take on our burdens and try and protect us emotionally.

The harsh reality of the day-to-day life for workers in this industry is brutal.

Speaking on a BBC Radio 4 podcast, content moderators have revealed the mental effect of seeing thousands of disturbing images and videos.

One man, named only as Colin, said: "I felt like a robot that had been brutalised all day".

He added: "You're spending eight hours a day bashing yourself in the face with horrible imagery."

A woman who remained anonymous said that after working on content moderation "I wouldn't shake people's hands - if you have had the job I have had, you know people are nasty."

Another said after watching child pornography videos: "I might as well be a nun, there's no way I can even think about sex".

Content moderators often have to see thousands of disturbing images a day (file photo) (Image: E+)

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He said if you even tried to imagine the worst imaginable images, you wouldn't be able to, because the human brain is only wired to go as far as it is comfortable with.

Colin saw around 12,000 images a day, often many were from the 'dark web', the part of the internet that is only accessible by special software, allowing users and operators to remain anonymous or untraceable.

Colin told that he began to see the same awful images again and again, sometimes the 'worst imaginable'.

"You go home and think about it and think I didn't even flinch when I saw that image, then you're depressed that you don't feel anything," he said, sharing his personal thoughts on what it's like when you've been doing it for a while.

He questioned whether you can ever really be prepared to see the things you do in the job.

Some images content moderators have to filter through are from the dark web (file photo) (Image: The Image Bank)

The BBC podcast presented an interesting analogy with content moderation - comparing it to a tradition in folklore known as 'sin-eating'.

Dr Helen Frisby, an expert of history, folklore and material culture of death, dying and bereavement, spoke to the programme about 'sin-eating'.

She explained that when a person died, relatives would pay a 'sin-eater' who would receive bread and a drink over the dead body.

The folklore tradition symbolised the person ingesting the sins of the deceased, who would therefore be able to pass comfortably into the after-life.

Dr Helen Frisby shares her knowledge (Image: LinkedIn)

The podcast aired the idea that content moderation is seen by some as a similar concept to sin-eating, employing people to take the sins from the world.

Sarah T Roberts, an Assistant Professor in the department of information studies at the University of California, Los Angeles, has researched commercial content moderation.

She said people within the occupation are being "paid to take on social, moral and emotional baggage that all societies have".

Sarah T. Roberts is an Assistant Professor in the Department of Information Studies at UCLA (Image: BBC)

In her experience, workers feel isolated, ruminate on what they've seen and some even admitted they began drinking more.

One unnamed woman said, after the things she has seen: "I can't trust my kids to anybody anymore."

To give a picture of the vast amount of content that is to be moderated online, the show revealed that 400 hours of video are uploaded to YouTube per minute per day.

That's just one social media site.

Till Krause, an editor and filmmaker, has spoken to content moderators in Berlin about how their jobs affected their mental wellbeing.